Effect of rGO Coating on Interconnected Co3O4 Nanosheets and Improved Supercapacitive Behavior of Co3O4/rGO/NF Architecture

In this study, the effect of reduced graphene oxide (rGO) on interconnected Co3O4 nanosheets and the improved supercapacitive behaviors is reported. By optimizing the experimental parameters, we achieved a specific capacitance of ~1016.4 F g−1 for the Co3O4/rGO/NF (nickel foam) system at a current density of 1 A g−1. However, the Co3O4/NF structure without rGO only delivers a specific capacitance of ~520.0 F g−1 at the same current density. The stability test demonstrates that Co3O4/rGO/NF retains ~95.5% of the initial capacitance value even after 3000 charge–discharge cycles at a high current density of 7 A g−1. Further investigation reveals that capacitance improvement for the Co3O4/rGO/NF structure is mainly because of a higher specific surface area (~87.8 m2 g−1) and a more optimal mesoporous size (4–15 nm) compared to the corresponding values of 67.1 m2 g−1 and 6–25 nm, respectively, for the Co3O4/NF structure. rGO and the thinner Co3O4 nanosheets benefit from the strain relaxation during the charge and discharge processes, improving the cycling stability of Co3O4/rGO/NF.